The present invention relates to a method and apparatus for measuring the complex dielectric constant of a dielectric, and more particularly to a method and apparatus for measuring the complex dielectric constant of a dielectric which can measure the complex dielectric constant of a dielectric with high precision.
With an enhancement in the performance of various radio devices, there has been required a ceramics dielectric for a high frequency having a high performance in a high frequency band of several GHz or more. In general, the ceramics dielectric has been used as a circuit component in the form of a burned product obtained by burning a powder-like dielectric. Moreover, a composite dielectric obtained by mixing the powder-like dielectric and a resin at various ratios has also been used as the circuit component.
In order to develop the ceramics dielectric for a high frequency, accordingly, it is indispensable that the complex dielectric constant of the dielectric is measured as the dielectric characteristic of the dielectric corresponding to the state of a powder and a burned product.
A dielectric constant in the complex dielectric constant of the powder-like dielectric has been calculated as follows. For example, a container having a pair of electrodes provided to be opposed to each other at a constant interval is filled with the powder-like dielectric of which dielectric constant is to be measured, a voltage is applied to a portion between the electrodes, and the dielectric constant of a mixture obtained by mixing the powder-like dielectric and air is measured. Thus, the dielectric constant is calculated from the dielectric constant of the mixture which is thus measured (see Patent Document 1).
On the other hand, the complex dielectric constant of a powder-like dielectric molding formed by burning is generally measured by using a perturbation method, a cavity resonator method and a dielectric resonator method (see Non-Patent Documents 1, 2 and 3). In the perturbation method, the cavity resonator method and the dielectric resonator method, it is required that a dielectric molding to be a measuring object takes a predetermined shape defined by each of the measuring methods. For example, it is required that the dielectric to be the measuring object is formed like a slender bar in the perturbation method, a sheet in the cavity resonator method and a cylinder in the dielectric resonator method.
[Patent Document 1] JP-A-6-138076
[Non-Patent Document 1] Yasushi Iijima, “Electronic Monthly”, Shinko Shoji Co., Ltd., July 1998
[Non-Patent Document 2] JIS R 1627: 1996 “Method of Testing Dielectric Characteristic of Fine Ceramics for Microwave”, Japanese Standards Association, July 1996
[Non-Patent Document 3] JIS R 1641: 2002 “Method of Testing Microwave Dielectric Characteristic of Fine Ceramics Board”, Japanese Standards Association, January, 2002
In a conventional method of measuring the dielectric constant of a powder-like dielectric, however, in the case in which the dielectric constant of the powder-like dielectric is to be measured in a high frequency band of several GHz or more, the presence of a floating capacity and a floating reactance cannot be disregarded. As a result, there is a problem in that a whole measuring apparatus resonates and the dielectric constant of the powder-like dielectric cannot be thus measured with high precision. Moreover, there has not conventionally been known a practical method of measuring a dielectric loss tangent in the complex dielectric constant of the powder-like dielectric as desired.
On the other hand, although the dielectric molding can easily be formed cylindrically depending on the type of the dielectric, it is hard to form the dielectric molding to take the shape of a slender bar or a plate. Consequently, there is a problem in that the complex dielectric constant of the dielectric cannot be measured by using the perturbation method or the cavity resonator method. On the other hand, in the dielectric resonator method capable of measuring a cylindrical dielectric molding, there is a problem in that a dielectric constant and a dielectric loss tangent cannot be measured in a dielectric having a low dielectric constant in a complex dielectric constant, for example, a resin.